The present invention relates to a developer cartridge and an image forming apparatus.
Conventionally, in an image forming apparatus such as a printer, a copier, a facsimile, a MFP (Multi-functional Product), and the likes, for example, in a printer using an electro-photographic process, a photosensitive drum, a charging roller, a developing roller, a cleaning device, and the like, are integrally formed in an image forming unit (process cartridge) to improve maintenance property. Further, the image forming unit is provided to be attachable to and detachable from a main body of the printer; that is, an apparatus main body.
Specifically, in a color printer, a capacity of toner is limited due to a size of the printer. Further, it is required to store toner in a plurality of colors in a limited space. Accordingly, a toner cartridge is provided attachable to and detachable from a main body of an image forming unit while toner is contained in the toner cartridge. Further, the toner cartridge is replaced as toner is consumed. The toner cartridge is provided with an engagement portion at an end portion thereof in a longitudinal direction for engaging with the image forming unit main body, so that a position of the toner cartridge is determined with respect to the image forming unit main body.
In the color printer, it is necessary to form an image with a high-definition without color shift. When an image with a high-definition without color shift is formed, it is necessary to provide parts relating to a printing operation with high dimension accuracy and assembly accuracy. Specifically, it is necessary to attach with high accuracy the image forming unit in which attachment and detachment operations are executed (refer to Patent Reference). Patent Reference Japanese Patent Publication No. 2004-170790
In the conventional printer, the toner cartridge is positioned with respect to the image forming unit main body. Accordingly, a relative position of the toner cartridge and the image forming unit main body remains unchanged. However, when rotation bodies inside the image forming unit main body such as a photosensitive drum, a developing roller, or the like rotate during a formation of an image or a printing operation, the image forming unit main body may twist, thereby lowering image quality.
In view of the problems described above, an object of the present invention is to provide an image forming unit and an image forming apparatus capable of solving the problems of the conventional printer. In the image forming unit and the image forming apparatus, it is possible to prevent a main body of an image forming unit from twisting while forming an image, thereby improving image quality.
Further objects and advantages of the invention will be apparent from the following description of the invention.